1. Field of the Invention
The present invention relates to an agent for reducing the nephrotoxicity appearing in living bodies to which cyclosporin has been administered. More particularly, the present invention relates to an agent for reducing the nephrotoxicity caused by cyclosporin administration, which contains a particular organogermanium compound as an effective component.
2. Description of the Prior Art
Cyclosporin, which is a compound extracted from fungi in the soil, effectively suppresses a so-called rejection reaction which is the biggest problem in organ transplants, i.e., an immune reaction between transplanted organ and host and, as a further advantage, does not weaken the power of resistance of transplanted organs against viruses. Accordingly, cyclosporin is highly evaluated as a drug which has remarkably enhanced the possibility of organ transplant operations.
The immunosuppression effect of cyclosporin is striking. It is reported that the graft survival rate after one year when kidney transplant has been conducted using cyclosporin is about 80% when using cadaveric kidneys and about 93% when using living kidneys, showing a significant improvement over the control using no cyclosporin.
The biggest clinical problem in using cyclosporin, however, is its strong toxicity to the kidney. As an example, there is reported a case in which organ transplant was successfully conducted but the cyclosporin administered to suppress the rejection reaction reduced the functions of the transplanted kidney making it necessary to adopt artificial dialysis.
The nephrotoxicity caused by cyclosporin administration can be classified into acute toxicity and chronic toxicity. These toxicities appear in the form of reduced kidney function such as an increase in serum creatinine, decrease in creatinine clearance and the like. In the case of acute toxicity, kidney function can be restored by the stopping of cyclosporin administration. In the case of chronic toxicity, it is thought that chronic toxicity does not progress further when the cyclosporin administration is stopped, although the stopping does not improve the reduced kidney function. In any event, the cyclosporin administration must be stopped in some cases in order to avoid nephrotoxicity, however, this stoppage results in the restoration of immunological competence and the resultant appearance of a rejection reaction, which incurs the functional loss of the transplanted organ in some cases.